1. Field of the Invention
The present invention is directed to Solid Oxide Fuel Cells ("SOFC's"), and more particularly to an interconnect for use in solid oxide fuel cells.
2. Background Art
Two large barriers to market competitive SOFC's are interconnect functionality and cost. The design of a SOFC interconnect is important because the interconnect serves several functions, including, providing reactant gas separation and containment, providing mechanical support to the cells and providing a low resistance path for current to connect the cells in series. Although monolithic interconnects of lanthanum chromite and high chromium alloys have been used with some success, such interconnects have proven to be excessively costly and compromise certain aspects of interconnect functionality.
In particular, since the interconnect performs a multitude of functions, often it is necessary to compromise the performance of one function to enhance the performance with respect to another function of the interconnect. For example, the interconnect has an electrical function inasmuch as it provides a path by which to electrically connect cells in series, and the interconnect also has a mechanical function, namely, to provide mechanical support to the cell.
With respect to such functions, it is necessary to, for example, match coefficients of thermal expansion (CTE) between the cell and the interconnect, to provide support for the cell and also to facilitate gas containment. If the interconnect does not match the remainder of the cell with respect to the CTE, the structure may lose mechanical integrity and gas may leak out of the cell, thereby adversely affecting the efficiency of the cell. Often times, an interconnect, such as a monolithic interconnect that exhibits superior performance with respect to this mechanical function, may exhibit an unacceptable electrical conductive performance. Accordingly, to develop a suitable monolithic interconnect, it becomes necessary to sacrifice performance with respect to one function of the interconnect, such as the mechanical function, to increase performance with respect to another function of the interconnect, such as the electrical conductivity.